Change speed transmission

ABSTRACT

A change speed transmission comprises rotatable input and output drive assemblies which are selectively connected by friction gearing to transmit power between an engine shaft and a driven device at different speed ratios. A body of one of the assemblies defines one direct drive friction gear member and part of an epicyclic friction gear unit. The other assembly carries a shifting member which is movable between one position for engagement with the direct drive friction gear member and a second position for engaging the epicyclic gear unit to provide a speed change between the drive assemblies.

[ 1 Jan. 9, 1973 [54] CHANGE SPEED TRANSMISSION [76] Inventor: Walter H.Moorhead, 4939 Donald Avenue, Cleveland, Ohio 44143 221 Filed: Feb. 16,1971 21 Appl.No.: 115,686

1,190,662 7/1916 Matteucci ..74/798 Primary Examiner-Milton KaufmanAssistant Examiner-Thomas C. Perry Attorney-Watts, Hoffmann, Fisher &Heinke [57] ABSTRACT A change speed transmission comprises rotatableinput and output drive assemblies which are selectively connected byfriction gearing to transmit power between an engine shaft and a drivendevice at different speed ratios. A body of one of the assembliesdefines one direct drive friction gear member and part of an epicyclicfriction gear unit. The other assembly carries a shifting member whichis movable between one position for engagement with the direct drivefriction gear member and a second position for engaging the epicyclicgear unit to provide a speed change between the drive assemblies.

4 Claims, 4 Drawing Figures CHANGE SPEED TRANSMISSION BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates todrive transmissions and more particularly relates to change speed drivetransmissions utilizing friction gearing.

2. The Prior Art Prior art proposals for transmissions associated withsmall horsepower engines in power lawn mowers, gocarts, motor bikes,etc. have been of various types. Most of these transmissions were of thefriction drive type which enabled the transmissions to be disengagedwithout sophisticated clutching arrangements.

Many of these transmissions provided only a neutral" or disengagedcondition and a single speed ratio. One common type was a belttransmission in which a pulley was movable to enable a drive belt toslip in order to disengage the transmission. In other transmissionscentrifugally operated friction gears were employed. These transmissionswere disengaged at low engine speeds and were gradually engaged asengine speeds increased. In other transmissions, friction disc typeclutches were associated with centrifugally operated sprague-typeclutches which provided speed responsive engagement.

Change speed transmissions which could be utilized on vehicles of thetype referred to were generally sophisticated. Accordingly, the use ofchange speed transmissions in these vehicles has not been widespreadbecause the improvement in performance of the vehicles has not beenjustified by the increased vehicle cost.

SUMMARY OF THE INVENTION The present invention provides a simple,inexpensive and compact change speed transmission which is particularlyadapted for use with small horsepower engines of the type used in powerlawn mowers, go-carts, motor bikes, etc. In a preferred embodiment, thenew transmission enables a driven device to be driven from an engineshaft through two speed ratios as well as providing a neutral ordisengaged condition in which the driven device is disconnected from theengine.

The new transmission includes an input drive assembly, an output driveassembly, friction gearing between the assemblies and a shiftingmechanism enabling the output drive assembly to be driven in a selectedone of two speed ratios relative to the input member. The shiftingmechanism also enables the input and output drive assemblies to bedisconnected.

One of the drive assemblies includes a body member defining a frictiongear member and a part of an epicyclic friction gear unit. The otherdrive assembly carries a movable shifting member which, when in oneposition, engages the friction gear member to provide a drivingconnection between the assemblies at one speed ratio. The shiftingmember is movable to a second position for engaging the epicyclic gearunit to establish a driving connection between the assemblies at asecond speed ratio.

In one preferred construction, the epicyclic friction gear unitcomprises a plurality of planetary rollers carried by a body which formsa cage for the rollers. The shifting member urges the rollers intofrictional engagement with a stationary race so that the body isrotated. The rotational speed of the body is less than the rotationalspeed of the shifting member when the epicyclic friction gear unit isengaged. The body preferably forms part of the output drive assembly sothat the epicyclic transmission provides a speed reduction between anengine output shaft and a driven device.

The body also forms the friction gear so that when the shifting memberengages the friction gear part of the body, the planetating rollers freewheel while a direct drive is provided by the friction gearing.

The epicyclic friction gear unit can be constructed to provide variousdesired speed ratios between the input and output drive assemblies. Inone preferred embodiment, the rollers are spherical bearing balls whichprovide a speed reduction of about one half speed. In anotherembodiment, wheel-like rollers are employed. These rollers providesections having different diameters. These sections are engaged withdifferent parts of the drive. This permits the speed ratio between theinput and output assemblies to be determined by the selection ofappropriate sized rollers.

In still another embodiment, the planetating rollers are engaged betweentapered or conical surfaces. The speed ratio between the input andoutput assemblies is controllable by selection of roller diameters.

A principal object of the present invention is the provision of a newand improved change speed transmission for small horsepower engineswhich is of simple, compact construction and can be fabricated frominexpensive, easily obtained parts.

Other objects and advantages of the present invention will becomeapparent from the following detailed description of preferredembodiments made with reference to the accompanying drawings which forma part of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of agasoline engine driven bike employing a transmission constructedaccording to the present invention;

FIG. 2 is a cross sectional view of a change speed transmissionembodying the present invention seen approximately from the planeindicated by the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary cross sectional view of a modified transmissionembodying the present invention; and,

FIG. 4 is a fragmentary cross sectional view of a further modifiedtransmission embodying the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A motor bike 10 embodyingthe present invention is illustrated in FIG. 1. The motor bike 10comprises a frame 12 supported by dirigible ground engaging wheels 14,16, and an internal combustion engine 18 supported on the frame whichdrives the rear wheel 16 via a chain drive 20. A transmission 22embodying the invention is connected between the engine 18 and the chaindrive 20. The motor bike 10 and associated elements, with the exceptionof the transmission 22, may be of any suitable or conventionalconstruction and therefore are shown schematically and are not describedin detail.

The transmission 22 provides two forward speed ratios for the bike aswell as a neutral or disengaged condition in which the engine 18 isdisconnected from the chain drive 20. Referring now to FIG. 2, thetransmission 22 comprises an input drive assembly 24, an output driveassembly 26 and friction gearing generally designated at 30 by which theassemblies 24, 26 can be drivingly connected. A shifting mechanism,generally designated at 32, controls operation of the friction gearing30 as is described in greater detail presently.

The transmission 22 is connected to the engine block 34 by screws 38 andstandoffs 40. The transmission 22 defines a housing which comprises arigid annular base plate 42 and a cup-like cover 44. The base plate 42and cover 44 are connected to each other and to the engine block by thescrews 38.

The input drive assembly 24 is connected to the engine output shaft 46for rotation with the shaft in the transmission housing. The inputassembly 24 comprises a cup-like bushing 48 connected to the engineshaft 46 by a key and keyway arrangement 50. The drive assembly furtherincludes a shifting member or rotor 52 which is nonrotatably connectedto the bushing 48 by suitable key and keyway arrangement 53. Theshifting member 52 is axially movable relative to the bushing 48 bysliding along the key and keyway 53. If desired, the key and keyway 53can be replaced by a spline or equivalent connection.

The output drive assembly is drivingly connected to the chain drive andis rotatably driven by the input drive assembly via the gearing 30. Theoutput assembly 26 comprises a body 54 having a sleeve 56 which projectsfrom the housing towards the engine block 34 and surrounds the engineshaft 46. A drive sprocket 57 for the chain is carried by the sleeve 56so that when the body 54 rotates, the chain is driven by the sprocket. Aflange 58 extends radially from the body 54 towards the inner peripheryof the base plate 42. A shoulder 60 is formed in the flange 58 adjacentthe inner periphery of the base plate 42 and a running seal 62 isprovided between the flange shoulder 60 and the base plate to seal theinterior of the housing. An annular flange part 64 extends radiallyoutwardly from the shoulder 60. The body 54 further includes an annularfriction gear ring 65 which projects axially from the flange 58 into thehousing.

The friction gear ring 65 cooperates with the shifting member 52 on theinput drive of the assembly to provide a direct drive friction gearconnection between the input and output drive assemblies. The ring 65abuts the flange part 64 and is connected to the flange part by screws66. The ring 65 has a generally conical internal surface 68 whichsurrounds the shifting member 52 and which carries suitable frictionmaterial defining an internal conical friction surface 70. As is shownin FIG. 2, the conical surface 70 on the friction gear ring convergesproceeding away from the direction of the engine block 34. The shiftingmember 52 has a generally conical outer surface 72 which converges inthe same direction as the surface 70 of the ring 65 so that when theshifting member 52 is moved towards the right as viewed in FIG. 2, theconical surfaces 70, 72 mate to establish a direct friction drivebetween the shifting member 52 on the input assembly and the ring 65 ofthe output assembly. When this friction drive relationship isestablished, the sprocket 57 rotates at the same angu' lar velocity asthe engine shaft 46.

The body 54 also defines an output drive member of an epicyclic frictiongear unit 73. The epicyclic friction gear unit 73 in the preferredembodiment is operable to provide a speed reduction between the engineshaft 46 and the sprocket 57 and includes a plurality of planetaryrollers 74 which are spaced circumferentially about the flange part 64in openings 76 in the flange part. When the friction surfaces 70, 72 aredrivingly connected, the body 54 rotates with the rollers 74freewheeling on the base plate. The rollers 74 of FIG. 2 are bearingballs which are confined in the flange part 64 by spherical boundariesof the openings 76.

The shifting member 52 defines an annular pressure face 80 confrontingthe rollers 74. When the shifting member 52 is moved to the left as seenin FIG. 2, the pressure face 80 engages the rollers 74 and forces therollers against a stationary annular bearing surface portion 81 on thebase plate 42. Friction forces between the rollers and the surface 81cause the rollers to roll on the surface 81 and the drive from theengine output shaft 46 is transmitted through the shifting member 52 tothe rollers 74. When adequate pressure is established, the rollers 74orbit about the engine output shaft 46 at one half of the rotationalspeed of the shifting member 52. Consequently the cage formed by thebody 54 is driven by the rollers at about one half of the engine speed.Accordingly, the body 54 drives the sprocket 57 at a maximum of one halfof the angular velocity of the engine shaft.

The transmission 22 also provides a neutral or disengaged condition inwhich the sprocket 57 is disconnected from the engine output shaft 46.This condition occurs when the shifting member 52 is between itspositions engaging the friction gear ring 65 and the rollers 74 of theepicyclic gear unit 73. In operation, the shifting member 52 is moved toits neutral condition for starting the engine. When the enginehasstarted, the shifting member 52 is moved to engage the rollers 74 toprovide a low gear for the motor bike. The epicyclic gear unit 73 isgradually engaged so that the bike 10 gradually accelerates. When thebike has attained a desired speed, the shifting member 52 is moved tothe right to engage the surfaces 70, 72 of the direct drive frictiongearing. The bike 10 is thereafter propelled in the high gear range.

The shifting member 52 is operated between its positions by the shiftmechanism 32. In a preferred embodiment, the shift mechanism 32 includesa foot operated shifting pedal 82 (FIG. 1) which, when released,provides for a normally direct drive from the engine shaft to thesprocket. When the pedal 82 is released, the shifting member 52 is urgedinto engagement with the ring 65 by biasing springs 86 which arepreferablycompression springs engaged between a radial flange 88 on thebushing 48 and sockets 90 in the shifting member 52. The compressionsprings 86 provide sufficient pressure to assure tight frictionalengagement between the shifting member 52 and the ring 65.

When the pedal 82 is depressed, the shifting member 52 is shifted to theleft as seen in FIG. 2 against the bias of the springs 86 and away fromthe gear ring 65. In the preferred embodiment, the member 52 is shiftedby a cam assembly including a stationary cam plate 94 which is connectedto the cover 44 by screws 95. The pedal 82 is fixed to an annularrotatable cam member 96 by a pedal support arm 98 which extends into thehousing through a cover 44 through a suitable dust seal 100. The camplate 94 and the cam member 96 each have mating circular inclined planecam sections which define engaged cam faces 101, 102.

When the pedal is depressed, the cam member 96 rotates relative to thecam plate 94 resulting in the cam member 96 moving toward the left asseen in FIG. 2. The cam member 96 has a bearing face 103 which engagesthe face 104 on the shifting member 52 so that when the cam member 96moves the shifting member 52 is likewise moved to the left towardengagement with the epicyclic gear unit 73. As soon as the shiftingmember 52 moves away from engagement with the ring 65, the transmissionis in its neutral position. As the pedal is further depressed, theshifting member 52 moves to engage the epicyclic gear unit resulting inthe sprocket 57 being driven in the low gear range. The downwardpressure on the pedal determined the pressure of engagement between theshifting member 52 and the rollers 74.

FIG. 3 shows another preferred embodiment of a transmission constructedaccording to the invention. The transmission which is illustrated inFIG. 3 employs a modified epicyclic drive unit but is otherwise similarto the transmission illustrated and described in reference to FIGS. 1and 2. Similar parts are therefore indicated by corresponding primedreference characters. The transmission 22' of FIG. 3 employs a modifiedbody 54 having a relatively heavy radially extending flange part 64. Anepicyclic gear unit 73' includes a plurality of planetating rollermembers 110 which are supported by radially extending axle shafts 112connected in the flange part 64. Each of the roller members 110 definesa wheel part 114 and hubs 116, 118 extending from opposite radial sidesof the wheel 114. The rollers 110 are rotatable with respect to the axleshafts 112 and the wheel part 114 rides on the baseplate 42' while thehubs 116, 118 ride on pressure surfaces of the shifting member 52'. Theshifting member 52 defines a pair of pressure faces 122, 124 at oppositesides of an annular groove 126 extending about the axis of rotation ofthe shifting member 52. The wheel part 114 extends into the groove 126and short of the base of the groove so that the wheel part rides solelyon the base plate. The pressure faces 122, 124 on either side of thegroove 126 engage the hubs 116, 118 respectively.

The hub 116 has a larger diameter than the hub 118 and the pressure face122 is spaced axially from the plane of the pressure face 124. In thisfashion the dif ference in angular velocity between the pressure faces122, 124 are accommodated and the roller members 110 are rotated by theshifting member 52' without slipping between the pressure faces 122 or124 and the hubs 116, 118 respectively. Slipping might otherwise occurbecause of the difference of distance from the center of rotation of theshifting member 52 between the pressure faces.

The use of roller members 110 enables the gear reduction between theengine shaft and the sprocket to the controlled according to thediameters of the wheel part 114 and the hubs 116, 118. Accordingly, itshould be apparent that changing the configuration of the roller willprovide different ratios as may be desired for the equipment for whichthe transmission is associated.

FIG. 4 is a partial fragmentary view of still another modification of atransmission embodying the invention. Modified parts corresponding toparts referred to above are shown by similar double primed referencecharacters. The epicyclic friction gear arrangement of FIG. 4 employs aplurality of circumferentially spaced ball type rollers which aredisposed between conical pressure surfaces 132, 134 formed on the baseplate 42" and shifting member 52", respectively. The gear reductionprovided by the epicyclic gear unit 73" can be altered by changing thediametral size of the balls carried by the body 54". As the diametralsize of the rollers is increased, the speed reduction through the gearunit 73" is reduced. The remaining parts of the transmission 22" of FiG.4 are similar in function and construction to corresponding partsdescribed above and therefore are not described in further detail.

Although more than one embodiment of the invention has been illustratedand described, the present invention is not to be considered limited tothe precise constructions shown. Other adaptations, modifications anduses of the invention may become apparent to persons skilled in this artand it is the intention to cover all such adaptations, modifications anduses which come within the scope of the appended claims.

What is claimed is:

l. A transmission comprising:

a. a housing;

b. an input member supported by said housing and rotatable about an axisextending through said housing;

c. an output member rotatable about said axis;

(1. one of said members being surrounded by at least a portion of theother member; and,

e. a change speed transmission means for transmitting drive from saidinput member to said output member comprising; I l. a shifting membersurrounding a portion of said one of said input or output members;

2. connecting means between said shifting member and said one input oroutput member for preventing relative rotation between said shiftingmember and said one input or output member and enabling sliding movementof said shifting member relative to said one input or output memberparallel to said axis;

3. said shifting member defining at least first and second drivetransmitting faces at spaced locations thereon; epicyclic friction drivemeans comprising a plurality of planetary roller elements rotatablysupported by the other input or output member, a stationary bearing facesupported by said housing for engagement by said roller elements, saidshifting member movable axially relative to said input and outputmembers to a first position for engaging said roller elements betweensaid bearing face and one of said first and second drive transmittingfaces whereby drive is transmitted from said input member to said outputmember with said input and output members rotating at different angularspeeds;

5. friction drive means comprising a friction surface supported by saidother input or output member and the other of said first and seconddrive transmitting faces, said shifting member movable axially relativeto said input and output members to a second position for engaging saidother drive transmitting face with said friction surface to transmitdrive from said input member to said output member with said input andoutput members rotating at the same angular speed when said frictionsurface engages said other drive transmitting face without slipping;and,

6. actuator means for effecting movement of said shifting member axiallyrelative to said input and means reacting between said one input oroutput member and said shifting member to urge said shifting memberaxially relative to said input and output members toward one of saidfirst and second positions.

3. The transmission claimed in claim 2 wherein said actuator meansfurther'comprises cam means comprising a first cam face fixed againstrotation with respect to said housing, a cam member comprising a secondcam face engaging said first cam face and rotatably movable with respectto said housing and said first cam face, and a speed changing memberconnected to said cam member for rotating said cam member relative tosaid first cam face, one of said cam faces axially movable relative tosaid input and output members for effecting axial movement of saidshifting member.

4. A transmission as claimed in claim 1 wherein said roller members aresupported for rotation with respect to said other input or output memberabout planetary axes extending radially from said axis, each 'rollermember comprising at least first and second cylindrical portions havingdifferent diametrical extents, one of said portions engageable with saidbearing face and the other of said portions engageable with said one ofsaid first and second drive transmitting faces.

1. A transmission comprising: a. a housing; b. an input member supported by said housing and rotatable about an axis extending through said housing; c. an output member rotatable about said axis; d. one of said members being surrounded by at least a portion of the other member; and, e. a change speed transmission means for transmitting drive from said input member to said output member comprising;
 1. a shifting member surrounding a portion of said one of said input or output members;
 2. connecting means between said shifting member and said one input or output member for preventing relative rotation between said shifting member and said one input or output member and enabling sliding movement of saId shifting member relative to said one input or output member parallel to said axis;
 3. said shifting member defining at least first and second drive transmitting faces at spaced locations thereon;
 4. epicyclic friction drive means comprising a plurality of planetary roller elements rotatably supported by the other input or output member, a stationary bearing face supported by said housing for engagement by said roller elements, said shifting member movable axially relative to said input and output members to a first position for engaging said roller elements between said bearing face and one of said first and second drive transmitting faces whereby drive is transmitted from said input member to said output member with said input and output members rotating at different angular speeds;
 5. friction drive means comprising a friction surface supported by said other input or output member and the other of said first and second drive transmitting faces, said shifting member movable axially relative to said input and output members to a second position for engaging said other drive transmitting face with said friction surface to transmit drive from said input member to said output member with said input and output members rotating at the same angular speed when said friction surface engages said other drive transmitting face without slipping; and,
 6. actuator means for effecting movement of said shifting member axially relative to said input and output members between said first and second positions, said actuator means also effective to position said shifting member axially between said first and second positions to interrupt drive transmission between said input and output members.
 2. The transmission claimed in claim 1 wherein said actuator means comprises spring means supported by said one of said input or output member for rotation therewith and with said shifting member, said spring means reacting between said one input or output member and said shifting member to urge said shifting member axially relative to said input and output members toward one of said first and second positions.
 2. connecting means between said shifting member and said one input or output member for preventing relative rotation between said shifting member and said one input or output member and enabling sliding movement of saId shifting member relative to said one input or output member parallel to said axis;
 3. said shifting member defining at least first and second drive transmitting faces at spaced locations thereon;
 3. The transmission claimed in claim 2 wherein said actuator means further comprises cam means comprising a first cam face fixed against rotation with respect to said housing, a cam member comprising a second cam face engaging said first cam face and rotatably movable with respect to said housing and said first cam face, and a speed changing member connected to said cam member for rotating said cam member relative to said first cam face, one of said cam faces axially movable relative to said input and output members for effecting axial movement of said shifting member.
 4. A transmission as claimed in claim 1 wherein said roller members are supported for rotation with respect to said other input or output member about planetary axes extending radially from said axis, each roller member comprising at least first and second cylindrical portions having different diametrical extents, one of said portions engageable with said bearing face and the other of said portions engageable with said one of said first and second drive transmitting faces.
 4. epicyclic friction drive means comprising a plurality of planetary roller elements rotatably supported by the other input or output member, a stationary bearing face supported by said housing for engagement by said roller elements, said shifting member movable axially relative to said input and output members to a first position for engaging said roller elements between said bearing face and one of said first and second drive transmitting faces whereby drive is transmitted from said input member to said output member with said input and output members rotating at different angular speeds;
 5. friction drive means comprising a friction surface supported by said other input or output member and the other of said first and second drive transmitting faces, said shifting member movable axially relative to said input and output members to a second position for engaging said other drive transmitting face with said friction surface to transmit drive from said input member to said output member with said input and output members rotating at the same angular speed when said friction surface engages said other drive transmitting face without slipping; and,
 6. actuator means for effecting movement of said shifting member axially relative to said input and output members between said first and second positions, said actuator means also effective to position said shifting member axially between said first and second positions to interrupt drive transmission between said input and output members. 